1. Field of the Invention
The invention generally relates to protective coverings and more particularly to thin film protective coatings for optical devices.
2. Background Information
One of the many problems associated with the design of optical materials is providing sufficient strength, hardness or durability to a particular material without negatively impacting the desired qualities or function of the underlying material. For example, transparent or translucent materials that are strengthened must be modified in a way that preserves the strength and durability to the materials without adversely affecting the desired optical characteristics of that particular item.
One of the methods for adding strength or durability to a particular device is to coat the device with a preselected material. However, one of the problems associated with typical coating arrangements is that simply thickening the coating on a particular device will, in many instances, alter desired characteristics. In addition, various other desired properties may not be achieved in single layer coatings due to excess thickness, resulting in high stress and poor microstructure. In an optical or transparent embodiment the placement of such a coating may also result in various undesired modifications or alterations to the optical or transparent properties of the device. In addition, the amount of strength that can be imparted to the material by the coating is many times limited by the inherent characteristics of the material itself. While various attempts have been made to address these problems, there still exists a need for materials and coatings that provide desired strength and durability to a portion of an optic device while allowing these optic devices to retain their desired functional properties.